<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <input type="file" name="img">
    <button>点击发送文件</button>
    <script>
        let inputEle = document.querySelector("input");
        let btnEle = document.querySelector("button");
        btnEle.onclick = function (){
            let xhr = new XMLHttpRequest();
            let form = new FormData();
            let img = inputEle.files[0] ; 
            console.log(img);
        }
    </script>
</body>
</html>